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The military has now taken power 12 times in the last eight decades

The first clear signs that Thailand could be destined for another spell of military rule came on Tuesday when martial law was declared.

The army denied it was taking over, saying the aim was purely "to preserve law and order".

But a quick look back in history shows that the military has often had a key role in shaping Thai politics.

Thursday's coup brings to 12 the number since the end of absolute monarchy in 1932, giving Thailand the dubious accolade of being one of the world's most coup-prone countries. Add to that seven attempted coups.

The right of the army to intervene in political affairs is even enshrined in law.

The leader of this latest coup, military chief General Prayuth Chan-Ocha, on Tuesday cited a 1914 act which gives the military the authority to declare martial law during a crisis.

Past interventions

Thailand has been under constitutional rule for more than 80 years, but for much of that time members of the army rather than civilians have held positions of power.

The first coup happened in June 1932, in a bloodless revolt that abolished absolute monarchy and introduced Thailand's first parliamentary elections.

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A coup in 2006 was also heralded by a heavy military presence in Bangkok

Six years later, military leader Luang Phibun Songkram became prime minister.

After a short-lived civilian administration following the end of World War Two, the military launched a coup in 1947 and remained in power until 1973.

Just three years of civilian rule followed, before a bloody crackdown on student protesters returned control to the army.

More coups and unstable coalition governments led by appointed prime ministers brought Thailand to 1992, when pro-democracy protesters filled the streets of Bangkok demanding a return to civilian rule.

King Bhumibol Adulyadej famously stepped in and asked the generals and pro-democracy leaders to reconcile their differences. They did, and Democrat Party leader Chuan Leekpai took power.

The next coup to reshape Thailand is at the root of the political impasse which led to the latest military takeover.

In 2006 the flamboyant Prime Minister Thaksin Shinawatra was toppled after being accused of corruption and abuse of power.

The army soon ceded power to a civilian government, but ever since there has been a power struggle.

On one side are those who support Mr Thaksin - and by extension his sister Yingluck, until recently the head of the now deposed government.

On the other are those who want Mr Thaksin's influence out of Thai politics for good.

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The army chief has suspended the constitution

Earlier this month, amid escalating violence between the two sides, the army warned that it "may need to come out... to restore peace and order".

General Prayuth said at the time that troops might have to end the violence "in full force".

His words have now in large part become reality: political gatherings are banned, a night-time curfew is in force, normal TV broadcasts have been disrupted and the constitution suspended.

The Thai army is once again playing a pivotal role in the nation's politics.